The essay aims at comparing differences in patterns of parliamentary recruitment for federal legislatures in Latin American countries. Those patterns as well as the political performance of state delegations were analyzed from the viewpoint of levels of stability in the control of seats. The Chilean House of Representatives is the case presenting the highest level of stable political careers in a context of moderate political turnover.. By contrast, Mexico and Argentina present high rates of political turnover among elected representatives, a condition facilitating the access of politicians lacking previous experience at the federal sphere of politics. Brazil is a intermediary case, displaying long periods of high rates of turnover, followed by reversals of such trend, as it occurs since 1998. When changes in the composition of party representation in federal legislatures resulting from voter's behavior are discarded, one may conclude that, with the exception of Chile, the high rates of political turnover are only marginally connected with electoral variations among the competing parties. Intra-party politics determining strategies for choosing and promoting candidates appear to be the most relevant variable explaining rates of parliamentary turnover.

Which relevance is there in the study of recruitment for the Houses of Representatives? One may raise the issue from another perspective, that is, does the knowledge of variations in the composition of state and party delegations - rates of turnover, identification of short or long careers, levels of expertise in the legislative process  increase our ability to understand and explain the dynamics of political representation? Beginning with Shugart and Carey (1992), the study of legislatures in Latin American countries became a reliable source of data supporting interpretations concerning the consolidation of new - and some not so new  poliarchies in the region. The predominance of the executive over the legislative branch of government is a feature well established by most scholars who detect, in accepted political practices prerogatives of executive authorities not granted by the respective national constitutions (Shugart and Carey, 1992). They also point out to aspects of the political process denoting such predominance: the power of agenda secured by the president, magnified by the problems of coordination among elected representatives (Figueiredo and Limongi, 1999); the relationship between presidential majority and presidential iniatives in legislation (Polina, Weldon and Lopez, 2000); the pattern of reactive behavior common to legislatures vis-à-vis the federal government (Cox and Morgenstern, 2002).

According to the institutionalist approach the way institutions are shaped affect the behavior of members. Given this assumption what data on political turnover and on patterns of political careers tell about the working of Latin American poliarchies? The issue may be approached from two different perspectives.

From one viewpoint it is reasonable to assume the connection between stabler political institutions, such as the House of Representatives, and incentives for stabler political careers, less defections and smaller turnover rates in scheduled elections. This trend is confirmed by long-run electoral results in western poliarchies. High turnover rates in those cases are exceptional and the trend to stability resumes in subsequent elections (Blondel, 1973, Best and Cotta, 2000).

High turnover rates were a common feature in American politics till the end of the 19th century, connected to high levels of social and geographical mobility. From this moment onwards declining numbers of first mandate representatives became the dominant trend, with few exceptions, such as the 37% turnover registered in 1933. From 1950 till the beginning of the 1990s the turnover rate varied around 16% (Polsby, 1968, Buckley, 1999, Brady, Cogan and Fiorina, 2000). The 1994 election for Congress brought along a high number of freshmen, that is, 14 Democrats and 73 Republicans. However, the total represented only 20% of the new House (Fenno, 1997, Aldrich and Rohde, 1997, Jacobson, 2000). The same pattern may be found in France, where high rates of political turnover are related to political crises. According to Gaxie (1993:85),

High turnover occurred again in 1958 when ¾ of the seats were occupied by new representatives. However, many of them were not new to party politics: some had previously competed in elections or had held public offices at the local administration level (Gaïti, 1999). In 1981 the Socialists were the majority in the National Assembly and the turnover rate was even higher, that is, 41,9%. But also in this case research on the personal data of the elected show that most of them had already a political career (maire, conseiller général, conseiller municipal). Once again the turnover was exceptional and had opened access to national politics to old hands in politics.

Political recruitment for the German Bundestag show a consistent downward longitudinal trend in turnover rates. From the high of 40% registered in the first two legislatures elected after the establishment of the Federal Republic (1949 and 1953), the numbers are 31% for 1957 down to the low of 21% in 1987. In 1990 the turnover rate of 35% may be explained by the commotion of the national unification. From 1994 onwards the turnover rates resumed the trend of low variation (Wessels, 1997).

The same stabilization trend may be found in parliaments of southern European countries. As expected, higher turnover rates were registered in the first two elections under democratic rules. They reached 50% to 60% in Italy, Spain, Greece and Portugal. However stabilization trends settle after the third election and stabler careers become a common feature of the political system (Liebert and Cotta, 1990, Morlino, 1992).

From another perspective and contrasting with the trend of lower rates of political turnover and stabler political careers, it is plausible to assume that, given a constitutional design restrictive to parliamentary initiatives in legislation, control over the government and political intermediation, the incentives to stable representative careers become jeopardized. The result may be intermittent careers and higher rates of political turnover. This may have happened in Brazil, according to Fabiano dos Santos (2000). He stresses the limitations imposed by the Federal Constitution of 1988 upon congressional scope of action, comparing it with the Constitution of 1946, and assumes that the changes adversely affected the patterns of political recruitment for the House of Representatives, that is, the rates of political turnover become higher and abler politicians are not keen on keeping the conquered seats.

Following this kind of argument one should not minimize the importance of feedback, that is, restrictions on legislative initiative and action and on the role of parliament as a sphere of political intermediation impose limits on individual efforts to building a stable political career; political recruitment may become a hazardous process, involving higher costs of obtaining and transmitting information needed to generate institutional loyalty and efficient coordination of political processes. Awareness of this kind of problem may have inspired Norris's comment: institutional approach have also paid little attention to the motivation and experience of candidates (1997:09).

Polsby (1968) and later Putnam (1976) stressed the connection between political turnover and professionalization of parliamentary representation. High rates of political turnover may have a positive effect on innovation and flexibility of political representation. But they may also difficult the consolidation of political leadership and the acquisition of legislative knowledge needed to ensure efficiency in specialized branches of legislation. As a side feature of this kind of problem Schepsle (1978) points out to the prevailing attitude among freshmen whose political concerns are mainly the ones directly connected with the interests of their constituencies. However shared expertise may bring about collective benefits for the institution as a whole because it maximizes the control of information needed for efficient monitoring of public policies by the representatives. The costs of obtaining information may be high and unapealing, unless the institution and the political rules provide incentives to individual specialization.

Long parliamentary careers also contribute to creating a body of knowledge shared by members of legislatures concerning accepted practices and patterns of behavior which reduce the element of uncertainty in the process of decision making . According to Tsebelis, if information is available, it will be easier for the individual to choose rationally than it would be the case if the payoffs are not clearly discernible. (1998: 46). This pool of knowlegde may have resulted from political socialization, that is, each representative learns the rules of the game by observing his peers's actual behavior. This practical knowledge provides the elements to be taken into account when individual calculations and definition of strategies must be made in situations requiring evaluation of consequences (support or denial of support by peers). From this viewpoint careful party recruitment of candidates is generally recommended in order to maximize the pool of shared knowledge concerning legislative institutions and practices.

Intermittent political careers, high rates of political turnover and hazardous recruitment are features of competitive politics which difficult the formation and consolidation of a pool of common knowledge to be shared by the whole body of representatives concerning policy-making processes and accepted legislative practices. The difficulty may be increased when the political system is federal. In this institutional format the composition of the national House of Representatives results from party competition in elections held at subnational political constituencies. Those constituencies may greatly vary in economic, social and cultural aspects. The transformation of state representatives into a national political elite, able to legislate for the whole country and in specialized matters requires learning and incentives to adopting values and behavior congruent with the office. Stable patterns of parliamentary recruitment become a strategic resource convertible into political power, political prestige and votes. By contrast, when lack of complete information and uncertainty concerning behavior of peers prevail, any level of concertation will depend upon the balance between incentives and sanctions offered to the individual, generally controled by other institutions such as the executive branch of government.

This paper focus on patterns of political careers in Houses of Representatives structured by different constitutional designs and frames of incentives and political opportunities in four Latin American countries: Argentina, Brazil, Chile and Mexico. It is assumed that stabler political careers and a high level of congruence in the distribution of party seats by region may be taken as evidence to favorable conditions for building a parliamentary elite committed to strengthening the legislative branch of government.

The countries under scrutiny were chosen because of their political relevance in the region and also because they offer good research matter, given the institutional variations they present. The following are stressed: Argentina, Brazil and Mexico adopt the federal format, Chile is a unitary State; their electoral systems are different (Table 1): proportional representation with closed list (Argentina), with open list (Brazil), a mix of majority/proportional representation (Mexico) and binominal proportional representation (Chile); the electoral cycles are different and connected to distinct party organizations and political traditions (Tables 2, 3, 4 e 5).

The findings here presented summarize data concerning parliamentary recruitment and electoral results over the recent period of the national history of each country (10 years). The number of legislatures in each case was defined by the electoral rules of the country, establishing the length of the parliamentary mandate: 3 years in Mexico, 4 years in Argentina, Brazil and Chile, another relevant rule being full substitution in every election or substitution of half of the House every two years, as is the rule in Argentina.

POLITICAL TURNOVER

Rates of turnover registered in every election is a basic variable in the study of parliamentary recruitment. The turnover rate denotes the number of first mandate elected representatives for the House of Representatives. It should be pointed out that research on this variable does not require comparing one legislature with the previous one. The approach here adopted is a non-sequential analysis of electoral results. This methodological procedure does not prevent taking into account the return of politicians who already have a previous political career albeit interrupted at the national level for a given length of time. The substitutes were not considered even when they occupied the seat during the legislature under study.

Interpreting the meaning of parliamentary turnover should assume explanations other than electoral defeat. The politician may have decided not to compete or may be pursuing a political career in other branches of government. It is not a easy task to determine the reasons why any given politician decides not to compete. However, plausible reasons are calculations concerning one's political strength in competitive elections and some evidence of forseeable defeat. According to Erickson, turnover also has implications for the retirement rate. When MPs anticipate electoral defeat, many may decide to retire voluntarily (1997:35). Some relevant elements in this calculation are: the public criticism of opinions held by the politician which may reflect on the vote, lack of financial support, loss of personal purpose for performing the role of member of parliament.

Research focusing on the American House of Representatives pointed out that electoral uncertainty is a very strong reason for political retirement. The mathematical formula developed by Black (1972) summarized this hypothesis: U= P(Bw) + (1-P) (B1) C. It is thus interpreted: the utility of competing is the result of the probability of winning (P), the gain derived from keeping the seat (Bw) compared to the gain of other activity available in case of defeat (B1), minus the cost of competing for reelection. The variation of Bw and C is the decisive element in the decision to compete. Fenno (1973) stressed the same sort of calculation to explain the decision to retire from electoral competition: uncertain victory and the opinion that one's priorities for the legislative agenda will not prevail. Moore and Hibbing (1998) have recently studied political turnover in American politics, which reached the high of 60% between 1946 and 1996. Their findings point out to the relevance of the following variables explaining the turnover trend: being a member of the minority party and few opportunities to hold prestigious offices in parliament1.

The interpretation of political retirement as a defensive option in a political environment adverse to the individual is well supported by findings comparing different political systems. The identification of the politicians elected for the national legislatures during the Fourth Republic in France reveals that 43% of them have held up to 5 mandates. This is indicative of a stable parliamentary elite. The political climate changed in the parliamentary elections of 1958 and 1962 when criticism of the Fourth Republic and of gaullist politics among the electorate allowed for significant political turnover. In the polarized climate of opinion, and forseeing predictable defeat, many of the grands noms voluntarily retired, a development that has not received enough attention in the study of the period (Birnbaum, 1977; Gaxie, 1993).

Later and also quite revealing is the circumstance of the 1994 national elections in Italy, when the partitocrazia collapsed (Guzzini, 1994). The traditional party system was then imploded, the electorate displaying strong disapproval of politicians denounced as criminals and generally avowing deep mistrust of political institutions. The end result was the sweeping redesign of the party system, the traditional Christian-Democrats becoming the Popular Party, the Socialist Party reduced to a very small political association, all these changes accompanied by the amazing electoral growth of new political groups such as the Forza Italia. The extensive political realignment caused, as expected, high rates of parliamentary turnover. In the 1994/96 elections the turnover rate reached 70%, a major change comparing to the rate varying around 35% registered since 1953 (Briquet, 1999; Bartolini and D'Alimonte, 1995). Two conditions may have accounted for the better chances for freshmen in the electoral competition for a parliamentary seat. First, the climate of political opinion unfavorable to well-known members of the current political class; second, the decision made by many of them not to compete. The underlying meaning of this retirement poses a interesting question of political interpretation, thus summarized by Briquet (1999:258):

The data reveal that 49% of members of parliament in 1994 competed for reelection, a lower rate than the 65% in 1987 and 54% in 1992. Only 21% of those who competed for reelection returned to the House of Representatives. The distribution of the retirement rate is uneven, affecting more severely the Christian  Democrats (63%) and less the Communists (34,6%). Only 12% of PPI candidates to reelection were elected, a worse result than the overall counting for the Italian Left (sinistros).

We turn now to the chosen Latin American countries. The time span covers elections held after the return to democratic regimes. For Chile and Argentina the study includes all elections held for the national parliament; for Brazil and Mexico, since the electoral calendar was respected during the authoritarian regimes, the time span is lengthier, beginning in the second half of the 1980s, when electoral competition among parties increased.

Taking stable poliarchies as a guiding reference, it is assumed that routinization of democratic procedures in new poliarchies should lead to diminishing rates of political turnover and to incentives to stabler parliamentary careers. Available data for the countries under study indicate variation in the expected pattern (Table 6).

The closest reproduction of the conventional pattern of recruitment is found in Chile. As expected, the turnover rate is high after 16 years without elections and regular congressional life. But beginning with the second legislature it fell consistently, the dominant trend being a high level of political return to the seat in the following election. Mexico and Argentina are the opposite cases. The high turnover rates in Mexico are easier to explain: in 1933 a constitutional provision forbade consecutive reelection for the national and provincial Houses of Representatives. The prohibition applies also to different forms of representation  majority or proportional and also to the position of substitute.The result of this rule is that turnover is total, that is, each legislature is entirely new in terms of membership. The cost of keeping party loyalty during the interim period explains the low rate of return in subsequent legislatures (Carbonell, 2000).

The case of Argentina calls for finer analysis. The turnover rates are lower than the Mexican ones, but the constitutional and electoral rules were designed to prevent this kind of political variation. Reelection is not forbidden and the selection of representatives follows the proportional principle with closed lists of candidates. These are rules stimulating stabler parliamentary careers. However, the electoral results show that in every election two out of three seats are occupied by freshmen. In 1983, 1989 and 1999 the president and the representatives were elected in the same electoral process, the elections happening after the mandate of a president either member of the Radical Party (Union Cívica Radical) or of the Peronist Party (Partido Justicialista). This condition may explain the high rate of parliamentary turnover. However, the same trend prevails when elections for the House of Representatives follow a different calendar, both at the national and at provincial levels (1985, 1987, 1991, 1993, 1997 and 2001). Addressing the issue, Jones (2000:165) takes into account some features of party politics: a) patterns of competition among party members which affect the level of difficulty of nomination for the provincial lists of candidates; b) electoral coalitions which may affect the ranking of individual members in the making of lists, notwithstanding their historical political prestige; c) individual calculations which take into account the costs of reelection and better options of career advancing by occupying offices in the executive branch of government or by competing directly for a seat in the National Congress (progressive ambition).

In Brazil parliamentary turnover is a permanent feature of the political system. The elections under study reveal that the turnover rates vary around 50% since 1946, the last of them held in 1994 (Marenco dos Santos, 2000). Empirical evidence indicates that most freshmen do not have previous political experience as representatives or incumbents of other kind of public office.. However, the election for the 1998 legislature brought back a higher number of members of the previous legislature. Indeed, it showed the lowest turnover rate in the last 52 years, including elections held during the authoritarian regime. The same trend is found in 2002 pointing out to a possible change of a historical pattern. The change may be thus summed up: growing number of representatives in their second or third mandate, diminishing number of freshmen, consolidation of parliamentary careers. Another striking feature of the Brazilian poliarchy is the significant number of representatives who have occupied offices in the executive branch of government. A hypothesis to be further examined refers to the impact of this pattern of political career in the lowering of political turnover in the federal House of Representatives. The shape of governamental and party institutions turned into accepted routine since the 1990s may be affecting the process of parliamentary recruitment towards greater levels of stabilization.

PARTY CONTRASTS IN PARLIAMENTARY TURNOVER

The study of parliamentary turnover based only on statistical data do not allow for assessing differences in party behavior that might be relevant in explaining the phenomenon. One of the issues to be addressed from this perspective may be thus summed up: does parliamentary turnover derive from practices in the political recruitment, adopted by the parties which control seats or is it a outcome of electoral realignments which affects the choice of voters and increases the chances of victory for political newcomers?

Jacobson (2000) interpreted the electoral results for the American House of Representatives in 1994 and came to the conclusion that the number of freshmen was due to electoral realignment in the Southern States, where vote for the Republicans increased. Fenno (1997) also assumes that turnover and political realignment are connected but offers another interpretation of the 1994 results. He points out that 40 years of political hegemony of Democrats in the House of Representatives induced a new generation of Republicans keener on ideological issues, who finally won the day in 1994. New parties competing in established parliamentary systems may also cause political realignments and give way to higher rates of political turnover (Best and Gaxie, 2000; Rush and Cromwell, 2000). Interpreting the variation in political turnover (the ratio freshmen/elected delegation) presents a further difficulty since the ratio denominator varies as a funtion of the party performance in each election2. Summing up: the political turnover within parties may have different causes: 1) freshmen may have access due to increase in the number of seats secured by the party; 2) unbalanced variation between the number of seats controlled by the party and the number of freshmen who get elected in one given election; 3) the loss of seats which alter the structure of opportunities for veterans and novices.

Statistical control of the effect connected to variation in the number of party seats in every legislature is possible by establishing the ratio between nominal turnover and the actual number of seats secured by each party.

When the flat rate of turnover is considered (REN), one may find that the Chilean political parties follow the same trend of diminishing numbers of freshmen in their delegations (Table 7). The exception is the small PRSD (5% of seats in 2001) and the independents. However, the corrected rates of turnover (RENdep) depict a more complex political scenario. The two leftist parties follow opposite trajectories: PPD is securing more seats and the Socialist Party is losing them. The positive variation is accounted by the turnover rates in the Partido por la Democracia which were high in 1993 and somewhat lower in 2001. The recruitment pattern among the Socialists is intriguing. They have lost half of the party seats between 1989 and 2001. But they offer few opportunities for newcomers (only 1 freshman among the 9 elected in 2001). Facing adverse electoral competition, the Socialists choose to boost the careers of veterans. The rightist parties UDI and RN opt for a different strategy. The high turnover rate registered in UDI is less striking when interpreted against the trend of increasing electoral weight of the party. The Christian Democrats who were dominant until 1997 do not provide safe electoral returns for the veterans since they are losing seats (the loss was significant in 2001). The turnover rate is also diminishing among them.

Indication for reelection is higher among members of conservative parties (UDI, RN), as well the probability of electoral success (Figure I). The practice of indicating incumbent representatives for reelection is also common among leftist parties and the Christian Democrats, albeit less ingrained as it is among conservatives. It should be pointed out though that only a small number of Christian Democrats is reelected.

The data on political recruitment in Argentina show that in 2001 all parties were affected by high rates of political turnover due to inter-party volatility (Table 8). In the period under study high rates of parliamentary turnover due to electoral variations are relevant only among provincial parties (the periods of expansion being the years of 1985, 1991 and 1999) and in the voting for the parliamentary representation of FREPASO since 1993. The data lead to the conclusion that the high rates of political turnover in Argentina, which affect every poltical faction after the demise of the authoritarian regime, are not explained by changes in the voters's party identification. The case of the strongest party, the Justicialista, is a good example. The statistical correction of the impact resulting from the variation in the number of seats secured in every election reveals that there is no significant oscillation in six elections, from 1985 till l995. In 1997 the party lost many seats due to defection of veterans to the newly created FREPASO. The inter-party turnover followed previous rates, meaning that the chances of indication for reelection or for competing for the first mandate were severely restricted. Only in 2001 the electoral recovery of the party allowed for a rate of parliamentary turnover higher than intra-party circulation. The UCR's trajectory deserves special attention: the party's parliamentary decline does not seem to prevent significant circulation of members in the lists for electoral competition.

The dissociation between parliamentary turnover and changes in the voters's choices of candidates in the lists presented by the competing parties is clearer when one considers the number of candidates occupying seats in one legislature who look for reelection and are successful (Figure 2). This control indicates that the most important criterion of selection (and, in the case of Argentina, of rejection) is the party decision when composing the list of candidates, the opinions of voters playing no decisive role. Statistically, in the two dominant Argentinian parties at least one in every five representatives completing the mandate will be included in the list for reelection. This proportion increases among provincial parties and in the FG-FREPASO's lists without altering the general trend. It deserves mention that the chances of reelection following the party's indication are higher in Argentina than it is the case in Brazil or Chile.

Until 1994 high rates of parliamentary turnover were common to all parties in Brazil, the highest numbers affecting PT, PDT and PTB (Table 9). The increase registered in 1994 may be due to electoral realignments, connected with the ongoing expansion of the vote in PT and the localized growth of PSDB's political weight. In 1998 this pattern is altered. The rates of parliamentary turnover clearly diminish among the elected delegations of PPB and PSDB and at a lower pace of PFL and PT. The turnover rate for PSDB would have been smaller but for the increase in the number of seats in competition. In the case of PT, variations in electoral behavior appear to be a variable explaining parliamentary turnover less decisive than intra-party competition in the composition of lists of candidates. The rates of political turnover for PMDB and PDT are stabler. However, due to decreasing in the number of seats they muster, the chances of following a stable career in the House of Representatives also decrease.

Electoral results in Mexico throughout the 1990s reveal a continuing declining trend of PRI, the steady strengthening of PAN, with a remarkable victory in 2000, when the party won the presidency, and the rise followed by decline of PRD. However the overall parliamentary turnover is not explained by changes in party preferences among the electorate (Table 10). The single most important cause of the phenomenon is the constitutional provision forbidding consecutive reelection. The politician may return to the House of Representatives after a three-year interim period, but occupying offices in other branches of the government is the strategic option to pursue a stable political career. Until 2000 PRI was the dominant party in control of the national government. It should be then expected higher rates of reelection among its members. From this perspective, comparing the median time span required for the return to the office of representative reveal a higher duration for PRI (5,7 years) and a faster pace for candidates of PRD (4,8 years) and PAN (3,6 years). Albeit the turnover rate in PRI be smaller than the ones registered in the other parties, the chances for any single priista to be part of a list for reelection is low. It is quite probable that the continuing reduction in the number of PRI seats in the House of Representatives gave way to tougher internal competition.

CONCLUDING REMARKS

Assuming that professionalising political careers in the legislative branch of government requires some amount of stability in the composition of lists of candidates, one may find important differences in the structure of political opportunities among the four Latin American countries under study. The lowest rate of political turnover is found in Chile, thus stimulating stabler parliamentary careers. Mexico and Argentina present the highest rates, thus offering greater opportunity for access to politicians lacking previous career in the national House of Representatives. Brazil stands in the middle, with a long history of high rates of political turnover followed by the recent lowering trend, beginning in 1998.

Given the idiosyncrasies of all possible institutional arrangements which may turn out to be a real puzzle for the researcher, it is a difficult task to determine the effective causes explaining the variation of this phenomenon. Incentives to investing in building and maintaining a political career in the House of Representatives are conditioned by one's evaluation on the relevance of political participation in the legislative process and the costs of electoral competition. From this perspective, political systems which allow wide margins of legislative and non-legislative power to the executive branch of government limiting the legislatures to reactive behavior most of the time give way to negative incentives for parliamentary careers and shrink the pool of political resources available to competing candidates in the electoral arena.

Despite the plausibility of this reasoning, some caution is advisable when establishing any kind of causality connecting institutional structure and political recruitment. Incumbents of legislative offices may control or have access to other types of political resources, such as political offices and captive audiences which may affect positively the results when competing for reelection.

It is not a easy task interpreting the elements which interact in electoral competitions. When the impact in the party delegation's turnover caused by changes in electoral preferences of the electorate is controlled (Figures 3, 4 and 5), it turns out that, with the exception of Chile, the high rates of parliamentary turnover are only marginally accountable by variations among the parties. Empirical findings point out to greater weight of intra-party decisions and electoral strategies in explaining the rates of parliamentary turnover. The influence of electoral rules should also be taken into account. It is to be expected that a set of rules restricting the access to freshmen and stimulating the decision to look for reelection among the present holders of mandates strongly determined the configuration of parliamentary representation. According to this assumption, proportional representation with closed lists of candidates should facilitate securing the seat in successive elections, especially in the case of low inter- party turnover. By contrast, open lists of candidates are seen as incentive to competition among parties. When this sort of interpretation is applied to understanding the Brazilian and Argentinian patterns the results appear contradictory. Some caution is advised thus when predicting electoral behavior based on prevailing electoral rules.

The Mexican case offers the opportunity of comparing electoral results based on majority and proportional formulae, under stable political institutions (Table 11). Taking into account that political return is a rare event, it is possible to calculate its probability according different electoral principles. For the members of the then governing party PRI the electoral principle did not alter the established rate of probability of returning to the House of Representatives. For members of opposition parties, the nominal indication to the list of candidates actually remained the only chance of reelection. Besides the known restrictions connected to the majority rule, the prohibition of consecutive reelection and the lack of access to offices in the executive branch of governement make the chances of victory in uninominal electoral competitions very low for candidates of opposition parties.

Norris (1997) points out to another condition that might explain different patterns of political recruitment, that is, the structure of political opportunities in unitary or federal political systems. A federal system offers a wider range of options for political careers at different levels of government. This political feature might explain the lower levels of parliamentary turnover in Chile, contrasting with Mexico and Argentina and, to a lesser extent, with Brazil. Besides the many options for individual careers at the federal, state and municipal institutions, the federal system further induces electoral competition among parties focused on the territorial distribution of political and administrative resources. Aiming at pursuing this line of reasoning, further research on political turnover at the subnational level is called for, in order to determine if party dispersion in local government (province or state units) widens the range of electoral competition and increases the number of competitors for seats at the national level.

The extension of time series of electoral data will allow for stronger conclusions and finer theorization concerning the impact of institutional changes, such as legislative prerogatives and electoral rules. The study of other countries such as Venezuela and Uruguay may offer additional elements to understanding the patterns of relationships between institutional change and political recruitment in Latin America.

JACOBSON, Gary. 2000. "Reversal of fortune: the transformation of US House of Representatives in the 1990s". In: BRADY, David; COGAN, John F and FIORINA, Morris. Continuity and change in House elections. Palo Alto: Stanford University Press.

1Members voluntary departing are often encouraged to do so by a precarious electoral situation (Moore and Hibbings, 1998:104) 2 This kind of problem may be lessened when agggregate data are used. There may be increases in the overall number of seats but it seldom happens. One may recall the 1987 addition of 100 seats to the Mexican House of Representatives (the event was not considered in the present research) or the 1994 addition of 10 seats to the Brazilian Congress.In the Brazilian instance if all the new seats were occupied by freshmen the overall impact on the rate of political turnover would be marginal, only 2 points in a rate varying around 55% and 60%.